Description ( provided by applicant): Since its introduction in 1999,West Nile Virus (WNV) has spread rapidly through out most of North America. It is likely that the epidemiology and maintenance ecology of WNV will differ substantially from region to region, and will change overtime as the infection moves from an epidemic to an endemic pattern of infection. The Principal Investigators of this proposal have collaborated closely over the past four years in a study of the ecology of Eastern Equine Encephalomyelitis(EEE) virus. We demonstrated that avian host choice by EEE vector mosquito esis highly restricted, and that certain species are targeted to a greater extent than predicted based upon their abundance. We have also found that peak periods in viral transmission correspond to periods of intense feeding upon certain avian hosts. We have also obtained preliminary data that suggest that vectors of WNV exhibit a similar pattern of avian host choice. The overall goal of this proposal will be to build upon our studies of the ecology of EEE transmission to develop a comprehensive picture of WNV transmission in the Southeastern USA. The specific aims of this proposal are: 1. To identify the most significant vectors for WNV in peri-urban and urban areas in South Central Alabama and to determine if the vector is involved in over-wintering of WNV in the Southeast. 2. To monitor WNV activity in the avifauna present at the study site, and to relate this activity to the interaction of the avifauna and vector mosquitoes at the site. We shall also monitor a well characterized songbird population to determine if there are subtle detrimental effects of WNV infection on the native avifauna. 3. To test the hypothesis that changes in the host-vector relationship are essential in triggering outbreaks of WNV.